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CVE Record

CVE-2021-29923: Go before 1.17 does not properly consider extraneous zero characters at the beginning of an IP address octe...

Go before 1.17 does not properly consider extraneous zero characters at the beginning of an IP address octet, which (in some situations) allows attackers to bypass access control that is based on IP addresses, because of unexpected octal interpretation. This affects net.ParseIP and net.ParseCIDR.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

Some Go versions before 1.17 could interpret IP addresses with leading zeroes differently than other software. If an application used Go’s IP parsing for allowlists, blocklists, or network trust decisions, an attacker might bypass those controls by supplying an ambiguous address.

Executive priority

Prioritize remediation for internet-facing or gateway services that make trust decisions from IP addresses. For internal applications without IP-based access controls, urgency is lower but still warrants upgrade during normal patch cycles.

Technical view

CVE-2021-29923 affects Go before 1.17, specifically net.ParseIP and net.ParseCIDR. The issue concerns extraneous leading zero characters in IP address octets and unexpected octal interpretation, creating parsing ambiguity that can undermine IP-based access-control logic.

Likely exposure

Exposure is most likely in applications built with Go before 1.17 that parse user-supplied IP addresses or CIDRs for authorization, proxy filtering, SSRF defenses, admin access, or network allow/deny decisions.

Exploitation context

The provided sources do not show CISA KEV listing or active exploitation evidence. Practical risk depends on whether ambiguous IP input reaches security decisions and whether another component interprets the same address differently.

Researcher notes

The source bundle identifies the vulnerable APIs and fixed version boundary but lacks CVSS, CWE, and detailed product impact. Treat downstream product exposure as vendor-specific unless confirmed by Fedora, Gentoo, Oracle, or other advisories.

Mitigation direction

  • Upgrade Go toolchains and rebuilt binaries to Go 1.17 or later where applicable.
  • Review Fedora, Gentoo, Oracle, and relevant vendor advisories for packaged fixes.
  • Avoid relying on ambiguous textual IP input for access-control decisions.
  • Normalize and validate IP addresses consistently before authorization checks.
  • Check vendor guidance for embedded or third-party Go components.

Validation and detection

  • Inventory services compiled with Go before 1.17.
  • Search code for net.ParseIP and net.ParseCIDR in security-sensitive paths.
  • Review allowlist, denylist, proxy, and SSRF protection logic using parsed IPs.
  • Test parsers with leading-zero IP inputs in a controlled environment.
  • Confirm rebuilt binaries use a fixed Go runtime/toolchain.
Prepared
Confidence
medium
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
10Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

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